Size and weight are important considerations in internal combustion engines. It is desirable to minimize the size and weight of an internal combustion engine of a given power output; conversely, it is desirable to maximize the power output for an internal combustion engine of a given size and weight. One way to increase the power output of an internal combustion engine is to increase the displacement and/or compression ratio of the engine, which generally will lead to an engine of increased size and weight. Internal combustion engines of minimal size and weight for a given horsepower are desirable, however, because decreased engine weight for a given power output means a more efficient use of engine fuel and/or increased vehicle acceleration capacity.
Today's high-power, high-compression engines require thick cylinder walls. However, this requirement is contrary to the desire to make engines more compact. The provision of heavy thick walls in block castings all the way down the cylinder from the combustion chamber end to the lower end increases the size and weight of the block casting. In an effort to reduce engine size, cylinder walls have been cast in Siamese form, that is, shared between cylinders, but this can impede the effective use of coolant to cool the engine. Thus, there is a need for engine block castings that can reduce the size and weight of an internal combustion engine and/or increase its power generating capability in a given size.